Sweeping apparatus

ABSTRACT

A housing has at least one compartment into which a rotatable brush deposits sweepings. The housing is mounted on wheels for movement in two mutually opposite directions and has at least one additional brush which is rotatable about an upright axis, being so mounted that the axis can tilt from vertical in dependence upon the direction in which the housing moves.

0 United States Patent 1191 1111 3,75e,215 Liebscher [4 1 Aug. 7, 1973 SWEEPING APPARATUS 2,782,434 2 1957 Parker et al. 15/42 x [75] Inventor: .ohannes Liebscher, Nassau/Lahn, FOREIGN PATENTS OR APPLICATIONS many 1,814,398 9/1970 Germany 15/42 [73] Assignee: Leifheit International Gunter 314,848 7/1929 Great Britain 15/87 L ifh it KG N /L b Germany 327,866 4/1930 Great Britain 15/50 R 'l I [221 FI ed y 1972 Primary Examiner-Edward L. Roberts PP N05 270,488 AttorneyMichael S. Striker [30] Foreign Application Priority Data [57] ABSTRACT J l 1 ,1971 P 1 4 93.4

u y 0 Germany 2 3 4 A housmg has at least one compartment mto whlch a 521 US. Cl 15/42 15/79 15/87 unable brush deP"sits sweepinfls- The using is 51 1m. (:1. A471 11/35 A47i 11/14 wheels mutual'y [58] Field of Search l5/4 2 79 87 49 Posite directions and has at least one additional brush which is rotatable about an upright axis, being so [56] Reterences Cited mounted that the axis can tilt from vertical in depen- UNITED STATES PATENTS dence upon the direction in which the housing moves.

500,976 7/1892 Tangenberg .1. 15/42 14 Claims, 7 Drawing Figures PATENTEBAus 7191s 3 750 215 sum 1 OF 3 PATENTEEALE 3,750,215

SHEET 2 [IF 3 PATENTEL 71973 3.750.215

SHEET 3 OF 3 SWEEPING APPARATUS BACKGROUND OF THE INVENTION The'present-invention relates generally to a sweeping apparatus, and more particularly to a sweeping apparatus using one or more brush rollers for sweeping purposes.

Suchapparatus is'basically known. It utilizes a housing provided with one or more compartments for sweepings, and has one or more brush rollers which, when the housing moves over a surface to be swept, rotates, picking up the sweepings and depositing them in the compartment or compartments. It is also known to provide one or. more substantially cup-shaped additional brushes whose purpose is to effect sweeping of those areas which are not-swept by the main brush 'roller, that is lateral areas. The concept behind this is fectiveness of .sweeping by the additional brushes is therefore only minimal.

Attempts have been made to overcome the problem in that the additional brushes are coupled by suitable gears with the .drive rollers of the housing, the gears being alternately engageable with the additional brushes independence upon the direction of move- .ment of the'housing, with the concept being that the *brushes should turn only in one direction irrespective of :the direction of advancement of the housing. However, this solution is evidently very complicated and therefore expensive, aside from the fact that experience-has shown it to be susceptible to malfunctions. In addition the high frictional resistance in the gears provided for the purpose make the arrangement difficult to operate and-the brushes will not turn freely enough to provide proper sweeping.

SUMMARY OF THE INVENTION It is,-accordingly, a general object of the invention to overcome the disadvantages of the prior art.

More particularly it is an object of the present invention-to provide an improved sweeping apparatus of the type mentioned above which is notpossessed of these disadvantages. I Another object of the invention is to provide such an improvedsweeping apparatus which achieves'the improvement in a simpleand reliable manner.

In pursuance of these objects, and of others which will-become apparent hereafter, one feature of the invention residesin a sweeping apparatus, briefly stated, in a combination comprising housing means having at least one compartment, wheel means mounting the housing meansvfor movement over a surface and being rotatable about respectiveparallel first axis for permitting movement of said housing means in two mutually opposite'directions, and brush roller means operative for sweeping solids into the compartment in response to rotation of the wheel means. At least one additional brush is provided, being rotatable about an upright second axis and mounting means mounts the additional brush so that the second axis thereof tilts in one or the other of said directions in dependence upon the direction of rotation of the wheel means.

With this construction opposite portions of the annulus of bristles provided on the additional brush will come in contact with the surface to be swept, as the direction of advancement of the housing is changed. Thus, always the inwardly facing portion of the bristle annulus will become active for sweeping purposes at any given time, whereas the outwardly facing portion of the bristle annulus that is the one located at the side of the axis of rotation which is away from the firstmentioned portionwill be lifted off the surface so that as a result the sweepings engaged by the brush will always be swept toward the interior of the housing and towards the brush roller which engages it and conveys it to the sweeping compartment. This means that the additional brush is operative for proper sweeping irrespective of the direction of advancement of the housing, and displacement of the sweepings outwardly away from the housing is avoided. The sweeping effectiveness is therefore substantially increased over what is known in the prior art.

It is advantageous to associate a drive wheel with the additional brush, in order to assure that it will be properly driven even under the most disadvantageous operating circumstances. The additional brush and the drive wheel may each be provided with a shaft fixedly connected with the brush and drive wheel, respectively, being coupled in suitable manner so as to have a motion-transmitting relationship and being journalled in a common journalling element. Because the axis about which the additional brush rotates can tilt, and because of the aforementioned journalling of the two shafts in a common journalling element, the tilting moments necessary for changing the orientation of the axis of rotation of the additional brush can be automatically triggered via the friction in the journal between the shaft of the drive wheel and the journalling element, because when the direction of movement of the housing is changed, the direction of rotation of the drive wheel is also changed so that tilting can be effected as a function of this.

In order to further improve the desired action, and to avoid slip in the drive for the additional brush, the shaft of the additional brush is advantageously coupled with the shaft .of the drive wheel by a bevel gear drive which is preferably accommodated in the common journalling means for them, the bevel gear drive means being such that the drive wheel and the additional brush rotate in one and the same direction or sense. In order to accommodate the shafts of the drive wheel and the additional brush, which extends substantially normal with reference to one another, in conjunction with the elements of the motion-transmitting bevel gear in the common journalling element, it is advantageous to provide the wall bounding the journalling space of the journalling element on the side facing away from the drive wheel with a removable wall portion, the journalling portions being provided for the shaft of the additional brush and being constructed as recesses having an open side facing the edge bounding the journalling space and being closed by tongue-like portions of the movable wall portion when the latter is replaced. This means that the shaft of-the drive wheel can be inserted with its fixedly associated portion of the gear arrangement axially into the associated journal and can thereupon be nonrotatably connected with the drive wheel which is placed onto the shaft from the opposite side, whereas the shaft of the additional brush need merely be inserted radially into the journal recesses provided for it. when the removable wall portion is then put in place, these journal recesses are closed. The removable wall portion is preferably provided with engaging portions which embrace corresponding portions of the remaining wall bounding the journalling space.

Advantageously a bracket is provided on which the journal for the additional brush or brushes is pivotably mounted, with the bracket having limited elastically yieldable arms provided with stubs which engage in journal openings extending in parallelism with the axis of rotation of the wheels. This assures that the orientation of the axis of rotation of the additional brush can be changed with a minimum of force on the one hand, and on the other hand a most simple mounting is provided for the various components, a mounting which can also be readily disengaged for inspection, repair or replacement. The angled portion of the bracket which faces away from the drive wheel is advantageously inserted movably to a holding portion of the housing, so that it can be turned about a pivot axis extending transversely to the axis of rotation of the drive wheel and of the additional brush, and a springy element is provided which engages the bracket intermediate the arms thereof and supports it with respect to the upper side of the housing. This assures that the journalling element has sufficient freedom of movement so that the drive wheel associated with the additional brush can follow any unevennesses of the surface over which it moves, thus assuring proper driving engagement with this surface at all times even if the surface is uneven and substantial resistance exists to rotation of the brush, as is for instance the case in carpets with long naps.

The springy element which supports the bracket is advantageously configurated as a leaf spring having one end which is snapped into a slot in the bracket and inclined with respect to the latter. To prevent undesired displacement of the journalling means as a result of any forces resisting rotation of the brush, the arm of the bracket facing towards the drive wheel can be provided with a projection which is engaged in a vertical groove of a portion of the housing.

To assure, particularly when carpets or rugs are to be swept or brushed, that a limited accommodation of the position of the additional brush or brushes is possible with respect to conditions of the service to be swept, it is advantageous to provide the additional brush with a shaft of prismatic or otherwise non-circular crosssection, being accommodated with limited freedom of axial shifting movement in a sleeve which is turnably journalled in the journalling means and whose interior is configurated to accommodate the shaft of the additional brush non-rotatably but with the aforementioned freedom of axial displacement. This makes it possible for the additional brush to yield axially if and when necessary. It is advantageous if the shaft of the additional brush is longer than the sleeve, having a free end projecting outwardly of the latter and being provided at this free end with a larger cross-section than the interior cross-section of the sleeve. To permit insertion and removal of the shaft with respect to the sleeve the free end is advantageously provided with an axial slot so that it can be compressed to the extent necessary to permit it to slide through the center passage of the sleeve. This permits assembly and disassembly without the use of tools and with considerable speed.

It has also been found advantageous to configurate the body of the additional brush, carrying the annulus of bristles, at its side facing the surface to be swept with a convex configuration, with the apex of the convexity projecting beyond the bristle ends of the annulus of bristles. With this arrangement the body of the additional brush in the region of the apex of its convexity can be maintained in engagement with the surface to be swept, so that specially in the case of sweeping of carpets having a long nap the pressure acting upon the bristles is limited sufficiently to preclude mechanical damage. Furthermore, the forces necessary to effect the tilting of the axis of rotation of the additional brush are magnified by engagement with the surface in the manner described above, so that pivoting is assured even under difficult operating circumstances. To maintain the bending moments acting upon the shaft on which the additional brush is mounted, especially beneath the journal provided for the shaft, and in order to make it possible to utilize as weak (and materialsaving) as possible a shaft, the body of the additional brush is advantageously recessed in hollow cylindrical form at the side of its shaft, with the cross-section of the recess being larger than the cross-section of the associated journalling element, so that a lower journalling location of the additional brush can be as close as possible to the surface to be swept. This not only reduces the bending moments which can act upon the shaft located downwardly of the journalling location, but also reduces substantially the overall height with which the sweeping apparatus must be constructed.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention'itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a sweeping apparatus according to the present invention;

FIG. 2 is a bottom view of FIG. 1;

FIG. 3 is a section taken on line III-III of FIG. 2, showing the sweeping apparatus during movement in one direction;

FIG. 4 is a view similar to FIG. 3 but showing the sweeping apparatus during movement in the opposite direction to FIG. 3;

FIG. 5 is a vertical section taken on line V-V of FIG. 2;

FIG. 6 is a horizontal section taken on line VI-VI of FIG. 5; and

FIG. 7 is a top view of the additional brush unit of the illustrated embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing now in detail it will be seen that the illustrated sweeping apparatus has a housing 10 which is essentially composed in known manner of an annular frame 11 and an upper housing portion 12 which is fixed to the frame 11. The latter carries at the exterior a substantially U-shaped bracket 13 to which in conventional manner a non-illustrated handle such as a broom handle or the likeis connected by means of which the apparatus can be pushed to and fro over a surface to be swept. On the inner side of the apparatus the frame 11 carries the various components, that is the sweeping brushes and the wheels which support the apparatus for movement over the surface to be swept as well as for driving the sweeping brushes in rotation.

It will be seen that there is provided a brush'roller 14 which is intended to sweep up sweepings from the surface to .be-swept, and which extends with its longitudinal axis transverseto the intended direction of movement of the apparatus, having opposite ends which are turnably journalled in a bracket l6,'the latter being pivotablymountedin holding elements 15 and being vertically shiftable in guides provided for this-purpose. A

settingmember l9. acts in known manner upon the bracket l6via a control cam, so that it. can be raised andloweredfand thus permits a raising and lowering of the brush roller 14. Theengagement of the bracket 16 against the control camtrack of the member 19 isassuredxin known manner by spring elements.

Thus far theconstruction is entirely known-from the art and need not bediscussed in further detail.

To-provide for turning .of the brush roller with respect to the surface to be swept drive wheels 20 are frictionally associated with the brush. roller 14. They are mounted in. pairs at opposite sides of the end portions-of the shaft of the brush roller 14in the frame 11.

.Atnoppositesides 'of'the brush roller 14 there are also provided compartments 21 to accommodate the sweepings. These compartments 2-l1are provided with a bottom-portion.22 which covers the underside of the sweeping apparatus except for the openings for the wheels-and for the brushes. Thebottom portion 22 is removably .mounted at the frame 11, to permit (lischarge-of the sweepings from the compartments 21. Because in. the directionof advancement of the apparatusone compartment2lis located before and one compartmentll. is'located behind the brush roller 14 (irrespective ofwhich of the two mutually opposite dire'ctions-one considers), the sweepings picked up by the brush roller 14 will alwaysbe deposited in one or the 1 other of the compartments .21, irrespective of whether brush23 is-providedin eachof the front corner regions of theapparatus. Each of the additional brushes 23 has a substantially cup-shapedannulus of bristles and is tur-nable abouta substantial vertical axis, thesweeping areaencompassed by the respective annulus of bristles overlappingthesweeping area of the brush roller'l4 on theonehandand the side wall and front wall region of the housingontheother hand. Each of the brush rollers 23.. is operatively associated with av respective drive wheel 24, being coupled therewith to assure that the brushes 23 are properly driven in rotation. The wheels 24 are located adjacent the respectively associated ad ditional brushes 23 and each have a shaft with which it is fast, the shaft being journalled in a tubular journal 25 which is part of a journal element 26, the latter having a gear space 26' in which an angle drive 27 configurated as a bevel gear drive is mounted. At the same time the element 26 also serves as a journal for the respective additional brush 23. The gear drive 27 provides for the motion-transmitting connection between the shaft 28 of the respective wheel 24 and the shaft 29 (extending normal to the shaft 28) of the respective brush 23. The shaft 29 in the illustrated embodiment is of prismatic or otherwise non-circular cross-section and has limited freedom of axial shifting displacement in a sleeve of corresponding cross-section, so that it can shift in the sleeve 30 but cannot rotate with respect to the latter. The sleeve 30 carries one bevel gear 31 of the angle drive, whereas the other bevel gear 32 of the drive is formed on the free end of the shaft 28, although it could of course be separately provided and suitably secured thereto.

The journalling element 26 is in the illustrated embodiment composed of two parts, in such a manner that the space 26 can be made accessible at the end wall 33 facing away from the respective wheel 24. This end wall 33 is configurated as a cover and provided with engaging portions 34 which can engage with the cooperating portions 35 to retain the cover in place. The portions 34 have limited elastic deformation capability to permit engaging or disengaging.

The journal portions 36 for the-shaft 29 for the sleeve 30 thereof are open recesses provided in the element 26, so that the sleeve 30 can be inserted from the side where the cover is provided, before the cover is put in place. The cover 33 is provided with portions 37 which close the open sides of the recesses 36 when-the cover .33isin-place, sothat the sleeve 30 is radially supported from alldirections without being hindered in its free turning movement.

To permit insertion and removal of the shaft 29 into and from the sleeve 30, the shaft29 is provided inits portion which extends axially beyond the sleeve 30 with a thickened part 38, thus preventing withdrawal from the sleeve 30 except when the part 38 is compressed, a possibility existing to the axial slot 39, at which time the part 38 can in fact pass through the central passage of the sleeve 30. Once the part 38 has passed through the sleeve 30 it will elastically move apart and retain the shaft 29 in the sleeve 30 until it is again compressed for removal purposes.

In the exemplaryembodiment the portion of the shaft 29 located between the portion 38 and the actual brush body 40 is somewhat longer than the sleeve'30, in order to permit a certain axial and vertical displacement of the additional brush 23 during operation inaccommodation to the surface unevennesses of the surface being swept.

The brush body'40 of the respective brush 23 carries the cup-shaped annulus 23' of bristles, and'has a side facing towards the surface to be swept, with the side being convexly curved. The curvature is so selected that the apex thereof extends slightly beyond the-plane 40 is hollow cylindrically recessed, so that the outer region 40 carrying the annulus 23' partially surrounds the space 26.

The element 26 in turn is pivotably mounted on a bracket 41 of substantially U-shaped configuration. The bracket 41 has journal pins 42 at the free ends of its arms which engage in recesses 43 of the removably wall 33 on the one hand and in a sleeve 44 provided above the journal 25 of the shaft 28 on the element 26. Thus, a tilting axis is obtained for the element 26, which axis parallels the axis of the shaft 28. The arm 45 of the bracket 41 is provided with a journal recess 46 extending transversely to the tilting axis and engageable with a pin 47. In this manner a pivoting of the entire unit about an axis extending in the direction of advancement of the apparatus is possible. The arm 45 also carries a leaf spring 48 whose free arm projects in the direction towards the respective wheel 24 and springily engages the upper housing portion 12, thus pressing the unit mounting the respective additional brush 23 downwardly towards the surface to be swept and assuring that proper contact with the surface is obtained for the associated wheel 24, even if the surfaces are uneven.

The contact of the wheel 24 with the housing, especially with the housing portion 12 is to be avoided even when the unit of the respective additional brush 23 pivots counter or moves the counter to the action of the spring 48. To assure this the bracket 41 is provided in one of its arms as shown with a projection 49 which enters into a groove 50 of a portion 51 of the frame 11, with one end of the groove 50 being of wedge-shaped wider configuration.

Due to the friction of the shaft 29 in the associated journal, the reaction forces occurring in the angle drive and the ground contact of the body 40 there is obtained, in direction upon the direction of advancement of the apparatus, a pivoting of the axis about which the additional brushes 23 rotate, made possible by the mounting of the element 26. This pivoting assures that always that portion of the annulus 23 will contact in the surface in sweeping engagement therewith which faces forwardly in the direction in which the apparatus advances. The opposite portion which faces rearwardly in this direction is lifted off the surface. The portion which is in engagement with the surface under the cireumstances will be seen, upon inspection of the drawing, to be that portion which turns towards the center of the housing, that is that portion which is capable of advancing the sweepings towards the region of engagement by the rotating brush roller 14 which can pick 1 them up and transport them into the compartments 2].

During operation of the apparatus it is customary to move the same first in one direction and then in an opposite direction. Because the direction of rotation of the wheels 24 changes, and because the orientation of the axis of rotation of the additional brushes 23 pivots in the manner already discussed, always that portion of the respective bristle annulus 23 is in engagement which turns towards the center of the apparatus, that is which moves the sweepings towards the center. This assures that the sweepings engaged by the additional brushes will under all circumstances move towards the brush roller 14 so that the additional brushes will operate for proper sweeping effectiveness irrespective of the direction in which the apparatus is advanced at any time. The mirrow-symmetrical arrangement of the additional brushes 23 as illustrated assures that portions of the surface can be swept at all times which cannot be directly reached by the main brush roller 14.

it is clear, of course, that the various modifications may be made in the illustrated exemplary embodiment without departing from the scope and intent of the present invention. For instance, only a single additional brush 23 could be provided in one corner region of the housing, or more than the two illustrated additional brushes 23 could be provided, just as more than two of the brush rollers 14 could be utilized. Also, the housing as well as the compartments 21 could be configurated differently.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a sweeping apparatus, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. In a sweeping apparatus, a combination comprising housing means having at least one compartment; wheel means mounting said housing means for movement over a surface and being rotatable about respective parallel first axes for permitting movement of said housing means in two mutually opposite directions; brush roller means operative for sweeping solids into said compartment in response to rotation of said wheel means; at least one additional brush rotatable about an upright second axis; and mounting means mounting said additional brush so that said second axis thereof tilts in one or the other of said directions in dependence upon the direction of rotation of said wheel means.

2. A combination as defined in claim 1, at least one wheel of said wheel means having a first shaft fixed therewith, and said additional brush having a second shaft fixed therewith; further comprising joumalling means joumalling said shafts jointly for rotation; and motion-transmitting means for transmitting motion from said one wheel to said additional brush.

3. A combination as defined in claim 2, said motiontransmitting means comprising a bevel gear drive operative for effecting turning of said second shaft in the same sense as said first shaft.

4. A combination as defined in claim 3, said journal]- ing means having an interior space accommodating said bevel gear drive and being in part bounded by a removable wall portion at a side facing away from said one wheel; said journalling means further having journalling recesses for said second shaft, configurated as recesses each having a side open towards one edge bounding said space, and said wall portion having tongue-shaped sections which extend across said open sides.

5. A combination as defined in claim 4; further comprising engaging portions on said wall portion for releasably embracing cooperating parts of said journaliing means.

6. A combination as defined in claim 2, said housing having a bracket provided with arms having limited elastic yielding capability, and said mounting means being mounted on said bracket; and further comprising stub shafts associated with the respective arms and each engaging in an opening provided in said journaliing means in parallelism with said first axes.

7. A combination as defined in claim 6, said housing having a holding portion, and said bracket having a bracket portion remote from said one wheel and engaged by said holding portion for movement about a pivot axis extending transverse to said first axes and the axis of rotation of said additional brush.

8. A combination as defined in claim 7, further comprising a springy support element engaging said bracket intermediate the arms thereof and supporting it with reference to said housing means.

9. A combination as-defined in claim 8, said bracket having aslot, and said support element being a leaf spring inclined to said bracket and having one end portion received in said slot.

110. A combination as defined in claim 7, said bracket having one arm closer to said one wheel than the other arm and provided with a projection, and said housing means having an at least substantially vertical guide groove into which said projection extends.

11. A combination as defined in claim 1, said additional brush having a shaft of non-circular crosssection; and further comprising a sleeve accommodating said shaft with limited freedom of axial displacement and being itself journalled for rotation.

12. A combination as defined in claim 11, wherein said shaft extends axially beyond said sleeve and has an exposed free end whose cross-sectional dimension exceeds the inner diameter of said sleeve, said free end having an axial slot so as to permit its elastic inward deformation to thereby reduce the cross-sectional dimension at least to said inner diameter.

13. A combination as defined in claim 1, said additional brush having a body provided with a convex side adapted to face toward a surface to be swept, and at least one annulus of bristles provided on said body.

14.. A combination as defined in claim 13, said body being at least in part of interiorly hollow-cylindrical configuration. 

1. In a sweeping apparatus, a combination comprising housing means having at least one compartment; wheel means mounting said housing means for movement over a surface and being rotatable about respective parallel first axes for permitting movement of said housing means in two mutually opposite directions; brush roller means operative for sweeping solids into said compartment in response to rotation of said wheel means; at least one additional brush rotatable about an upright second axis; and mounting means mounting said additional brush so that said second axis thereof tilts in one or the other of said directions in dependence upon the direction of rotation of said wheel means.
 2. A combination as defined in claim 1, at least one wheel of said wheel means having a first shaft fixed therewith, and said additional brush having a second shaft fixed therewith; further comprising journalling means journalling said shafts jointly for rotation; and motion-transmitting means for transmitting motion from said one wheel to said additional brush.
 3. A combination as defined in claim 2, said motion-transmitting means comprising a bevel Gear drive operative for effecting turning of said second shaft in the same sense as said first shaft.
 4. A combination as defined in claim 3, said journalling means having an interior space accommodating said bevel gear drive and being in part bounded by a removable wall portion at a side facing away from said one wheel; said journalling means further having journalling recesses for said second shaft, configurated as recesses each having a side open towards one edge bounding said space, and said wall portion having tongue-shaped sections which extend across said open sides.
 5. A combination as defined in claim 4; further comprising engaging portions on said wall portion for releasably embracing cooperating parts of said journalling means.
 6. A combination as defined in claim 2, said housing having a bracket provided with arms having limited elastic yielding capability, and said mounting means being mounted on said bracket; and further comprising stub shafts associated with the respective arms and each engaging in an opening provided in said journalling means in parallelism with said first axes.
 7. A combination as defined in claim 6, said housing having a holding portion, and said bracket having a bracket portion remote from said one wheel and engaged by said holding portion for movement about a pivot axis extending transverse to said first axes and the axis of rotation of said additional brush.
 8. A combination as defined in claim 7, further comprising a springy support element engaging said bracket intermediate the arms thereof and supporting it with reference to said housing means.
 9. A combination as defined in claim 8, said bracket having a slot, and said support element being a leaf spring inclined to said bracket and having one end portion received in said slot.
 10. A combination as defined in claim 7, said bracket having one arm closer to said one wheel than the other arm and provided with a projection, and said housing means having an at least substantially vertical guide groove into which said projection extends.
 11. A combination as defined in claim 1, said additional brush having a shaft of non-circular cross-section; and further comprising a sleeve accommodating said shaft with limited freedom of axial displacement and being itself journalled for rotation.
 12. A combination as defined in claim 11, wherein said shaft extends axially beyond said sleeve and has an exposed free end whose cross-sectional dimension exceeds the inner diameter of said sleeve, said free end having an axial slot so as to permit its elastic inward deformation to thereby reduce the cross-sectional dimension at least to said inner diameter.
 13. A combination as defined in claim 1, said additional brush having a body provided with a convex side adapted to face toward a surface to be swept, and at least one annulus of bristles provided on said body.
 14. A combination as defined in claim 13, said body being at least in part of interiorly hollow-cylindrical configuration. 